Analysis and design of composite curved frames

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Virginia Tech

In this work, methods for rapid analysis and design of composite curved C-section frames subjected to axial tensile loading are developed. Failure is predicted using polynomial in-plane and interlaminar failure criteria. Interlaminar stresses can be directly computed only from three-dimensional finite element models, but the computational expense of these models is prohibitive. Therefore, approximate two-dimensional analysis methods are used here to predict interlaminar stresses in the curved corner regions between the web and flanges and at the free edges of the flanges. A response surface design approach is used to approximate the failure response using a minimum number of finite element analyses. Large degree of freedom 2D/3D global/local finite element models are selectively used in conjunction with the smaller 2D shell element models in the design process to improve the response surface polynomials. This combined use of simple and complex analyses is known as variable complexity modeling.

Two design case studies are conducted, one with two design variables and one with five design variables. Three different objective function formulations are used in the two design variable case, minimum weight, maximum strength, and combined minimum weight and maximum strength. Only the minimum weight formulation is used in the five design variable case due to the complexity of the design space. The design studies demonstrate the accuracy and efficiency of the proposed approach.